Let's just say that The Flash in the CW TV show, Barry just runs fast for the heck of things and all that; the fact that he can run this fast, here and there with all mixed up equations and other problem solving barriers that we compare to events happening in every episode, let's just all come to a conclusion that The Flash's speed is super fast; ffOf course faster than the speed of sound and a bullet — that is all we need to know...
The episode where Barry saves Joe from that lightning entering the roof of the car, an average speed of lightning is around 300,000 meters/s at least — or I think so. Giving Barry running close to around Mach 2,900 or faster. I believe my Math was way off there, someone please correct me if I was just wrong there.
Again, The Flash's speed can vary and it is debatable according to his willpower and mind altering his speed-force. Flash generally runs around Mach 2 or 3 — pretty fast enough — but when he gets super angry or needs to run for something important, he can go 4 times that of his general "jog" as you can say.
Don't forget that speed of sound is around 750-60 mph, so just think about it if you were in a Bugatti moving 275 mph — top speed — you'd probably pass out...
Right now in season 2 episode 18, Spoiler Flash is faster than Zoom, and if Zoom can catch hundreds of bullets with only one hand... well Flash is just over that folks — to the point where he already be catching lightning and create speed mirages; being able to be in two to three places at once!